Galio's W (Bulwark) does not apply Windspeaker's Blessing mastery

As seen in the title, I tried out Galio with and without Windspeaker's Blessing mastery in a custom game and saw no difference. The mastery should have increased resistances by 15% (level 1 Bulwark => 30 Armor and MR * 0.15 = 4.5 bonus Armor and MR), but Ashe bot had 51 Armor and 60 MR both with and without the mastery.

The only reason I take any issue with this is because Bulwark's description says that "Galio shields an ally Champion, increasing their Armor and Magic Resistance...".

Were this mastery to apply, rank 5 Bulwark (90 Armor and MR) would grant a bonus 13.5 Armor and MR, and would (in my opinion) make Galio support a great option against a Corki lane, or even for any game with 2 or 3 magic damage-focused champions on the enemy team.